I'm trying to install a version of Centos onto my secondhand Dell poweredge 750 server..But i can not find any hard disk in the installation process.. so.. i tried to download the perc driver from dell.com but this is in .bin format.. and i can't get it to run during the installation.. any tips and trick on how to solve this?

If the CentOS 6 install doesn't find the controller then it's probably not supported and you would need a "driver disk" to get it supported. To be honest, a 750 is so old that it's probably not worth the effort - it'll eat so much electricity that it's performance per watt figures will make it uneconomical to run.

CentOS 5 died in March 2017 - migrate NOW!Full time Geek, part time moderator. Use the FAQ Luke

This is for my own website.. just wanting to learn little bit about linux, server, hosting aso.. and i just bought the server for next to nothing.. so i would hope i could get it fired up.. what you mean about driverdisk?

The Red hat enterprise is supported.. and i'm under the impression that redhat and centos is almost identikal?

Yes, CentOS is built from the RHEL source code so it should be compatible but that box is so old that it may well be RHEL 5 that had support for it. Both RHEL and CentOS 5 are dead, for more than a year, so don't install those.

CentOS 5 died in March 2017 - migrate NOW!Full time Geek, part time moderator. Use the FAQ Luke

You could check if there's any free sata ports on the motherboard. If there is, then you may cobble together something with a sata drive.For learning purposes, any old PC with an intel core processor should do.